Transformer with temperature controlled adjustable coupling



July 8, 1969 G. c;. MERKL 3,454,914

TRANSFORMER WITH TEMPERATURE CONTROLLED ADJUSTABLE COUPLING Filed Dec. 11, 1967 im i INVENTOR. GEO/Q 556, MEAZ/(L By 0, I Y

United States Patent 3,454,914 TRANSFORMER WITH TEMPERATURE CON- TROLLED ADJUSTABLE COUPLING George G. Merkl, 517 Boulevard, New Milford, NJ. 07616 Filed Dec. 11, 1967, Ser. No. 689,691 Int. Cl. H01f 27/10 U.S. Cl. 336-57 3 Claims ABSTRACT OF THE DISCLOSURE A three-ledged transformer wherein the central leg forms a magnetic shunt for decreasing the coupling between the windings on the two outer legs. The core material is an iron-nickel alloy containing approximately 29;;30% nickel by weight, the balance consisting essentially of iron. The decoupling central leg shunt, when heated, undergoes a reduction in magnetic permeability sol that its shunting or decoupling effect is minimized. When the centralleg is cooled, however, its decoupling effect increases so that the coefficient of coupling between the windings or "groups of windings on the two outer legs is greatly reduced.

The invention relates to a transformer comprising a three-legged core. Primary and secondary windings are mounted on the two outer legs. The third leg operates as a shunt which decouples the secondary winding or windings from the primary winding or windings. The core material is an iron-nickel alloy the magnetic permeability of which varies as a function of its temperature. The amount of decoupling between the primary andsecondary windings may thus be controlled by adjusting the temperature of the central leg independently of the rest of the core structure.

The invention is described in greater detail in the following specification with reference to the accompanying: drawing forming a part hereof.

Referring to the drawing:

FIGURE 1 is a diagrammatic perspective view of a transformer embodying the invention.

FIGURE 2 is a transverse sectional view of a laminated core structure taken along the line 2-2 of FIG. 1, looking in the direction of the arrows, and further illustrating a transformer similar to that of FIG. 1 immersed in a liquid temperature control medium.

The transformer comprises a three-legged core structure designated generally as and which is formed of an iron-nickel alloy containing approximately 29-30% nickel by weight, the balance consisting essentially of iron. Typical temperature-permeability characteristics of such a material are as follows:

Temperature, C. Flux density/cm. Permeability transformer core materials such as silicon steel.

3,454,914 Patented July 8, 1969 Fee .the secondary leg 12. The primary and secondary windings 18 and 19 may each comprise a plurality of separate sections, if desired. However, for simplicity of illustration, the primary winding 18 is shown as consisting of a single winding comprising lead wires 21 and 22 connected to terminals 23 and 24, respectively. Similarly, the secondary winding comprises lead wires 26 and 27 connected to terminals 28 and 29.

A length of metallic tubing such as copper tubing 30 is wound helically around the central shunt leg 13 of core'structure 10. The tubing 30 is used for varying the temperature of the shunt leg 13. The temperature of leg 13 may be raised by passing a heated fluid through the tubing 30 from fluid circulating unit 30A. The leg 13 may be cooled by passing a coolant through tubing 30. Tubing 30 may be insulated and energized as an electrical conductor to heat the leg 13. The use of alternating current of suitable frequency will heat the leg 13 by induction. The use of direct current will heat the leg 13 by resistive heating of the tubing 30. Alternatively, the tubing 30 may enclose a separate resistive heating element (not shown).

Where a permeability ratio of the order of 3:1 for the maximum and minimum permeabilities is sufficient for the central shunt leg 13, the core structure is preferably air cooled as shown in FIG. 1 and the shunt leg 13 operated at temperatures within the range from +25" C. to +50 C. (see table above). In order to prevent a general temperature rise of the core structure 10, the provision of a suitable blower (not shown) will be desirable.

If it is desired to utilize a permeability range of the order of 7 :1 in leg 13, a coolant bath should be provided as shown in FIG. 2. A liquid coolant 31 such as an oil is circulated through a closed housing 32 between an inlet 33 and an outlet 34. If desired, a gaseous coolant may be used. By maintaining the temperature of the coolant 31 at 20 C., an unheated permeability of 116.3 is obtainable in the core structure 10 including the shunt leg 13. Heating the leg 13 to +50 C. will reduce its permeability to 17.0 so that its shunting or decoupling effect will be greatly reduced with respect to that obtained with a permeability of 116.3 at its minimum temperature of -20 C. Except for the heated leg portion 13, the core structure 10 will have a general permeability of the order of approximately 116.3 because its operating temperature will be maintained at 20 C. by the coolant 31.

While I have shown and described what I believe to be the best embodiment of my invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A device of the class described, comprising: a magnetic core structure comprising at least three core portions, said structure further comprising at least one portion magnetically coupling two of said core portions each to the other subject to decoupling by the third one of said core portions, said decoupling increasing in magnitude with increasing permeability of said third core portion, said third core portion being formed of magnetic material the permeability of which may be varied by varying the temperature thereof, primary winding means on said first core portion; secondary winding means on said second core portion; and heat transfer control means positioned in thermally conductive relationship with respect to said third core portion for varying the temperature thereof to selectively vary the flux of said third core portion to control the secondary current output.

2. A device according to claim 1, wherein said third core portion is formed of an alloy consisting essentially of from 29% to 30% nickel, by weight, the balance being iron.

3. A device according to claim 2, further comprising a conductive heat transfer means in which said core structure is immersed, and means for circulating said heat transfer means, said heat transfer means being maintained at a temperature below normal room temperature.

References Cited UNITED STATES PATENTS Bartlett 336-160 XR Wehe 336155 XR Burnham 336-57 XR Chilowsky 336-155 XR Chilowsky 336-455 XR Bailey 336155 XR Postal 336-179 XR LEWIS H. MYERS, Primary Examiner.

T. J. KOZMA, Assistant Examiner.

US. Cl. X.R. 

